Subterranean geothermal, oil and gas, and water wells are frequently used to tap subterranean resources. Regardless of the well type, proper sealing of the well casing from the outside environment is important for safe and efficient function of the well. Incomplete or improper sealing can arise from initial incomplete formation or deterioration of the bond at the cement/casing interface or at the cement/rock interface. Such incomplete or improper sealing can result in costly and dangerous problems during active well use. For example, improperly or incomplete sealing of a subterranean petroleum well can lead to a lack of control for both production and injection into or out of a given formation. For instance, if the well is a petroleum injection well, the injection fluid can travel up the annulus and/or down the annulus and enter the formation at a point where it is not desired. In addition, production of unwanted water can occur along with desired oil and gas. This lack of a functioning annular seal can be very hard or impossible to remedy using conventional cement systems.
Currently available sealing techniques involve pumping Portland cement grouts into areas where the seal has been damaged or where leaking or fluid loss is occurring. One problem with this solution is that it typically requires that the cement left inside the casing be drilled back out, which can be a costly and time consuming operation. In addition, Portland cements may not be able to penetrate the small cracks in the existing cement and therefore not be able to completely fix the existing problem.